In the legacy Long Term Evolution (LTE) mobile telecommunication systems procedure for system information (SI) change notification and system information broadcast schemes have been well designed for use equipment (UE) to be informed of system information change and update UE stored system information. However, in the 5G system information is classified into two categories, the minimum SI (MSI) and other SI (OSI). The former is the most essential system information, such as the system information related to cell access, while the latter is the SI which is not included in minimum SI. Some of OSI may be periodically broadcasted the same way as in the LTE, and some of OSI may be delivered on demand, which is called the on-demand OSI. The on-demand OSI is not periodically broadcasted by the 5G base station called the gNB. Instead, the gNB provides on-demand SI when required. The gNB could proactively provide on-demand SI for some UEs in need. The gNB could reactively transmit on-demand SI when the gNB detects UEs' request on certain on-demand OSI.
The objective to have on-demand SI delivery is to enhance legacy approach to SI delivery. In the legacy LTE, system information is always broadcasted periodically. Periodically broadcasted system information causes periodic inter-cell interference, and thus limits the density of cell deployment. In addition, periodic broadcast reduces radio resource utilization since the gNB always broadcasts all system information even if there is no UE in the cell or even if some system information is not needed by any UE in the cell. Furthermore, periodically broadcasted system information is not good to discontinuous transmission (DTX) since the gNB always needs to do periodic broadcast. It is, therefore, desired to deliver on-demand OSI only when they are needed by some UEs to reduce unnecessary SI transmission.
Improvements and enhancements are required for on-demand system information delivery.